Leadframes are found in virtually all integrated circuit (IC) packages. Leadframes electrically connect IC dies to other electrical components within an IC package. Leadframes also connect electrical components in the IC package to electrical circuitry outside the IC package. In addition, leadframes act as a base structure upon which other IC components are mounted.
Leadframes are initially formed by etching or stamping a thin, flat sheet of metal (usually copper, aluminum, or gold) to form a leadframe strip. Each leadframe strip usually contains several longitudinally spaced apart leadframe panels. Each panel, in turn, comprises an array of integrally connected leadframes arranged in a rectangular grid that is bordered on all four sides by unformed portions of the leadframe strip. Each leadframe strip undergoes a series of processes that ultimately produce multiple, separate IC packages. Each IC package typically includes at least one leadframe, at least one die mounted on the leadframe and electrically connected to the leadframe, and a hard protective coating of cured mold compound. The mold compound covers and protects the leadframe and die(s) and any other package components. Portions of leadframe leads are exposed to enable connection of the IC package circuitry to outside circuitry.
The processes that a leadframe undergoes during IC package formation usually produce a number of defective IC packages. These defective IC packages must be detected and removed before the IC packages are shipped to customers.